English Abstract Marine phytoplankton in the world's oceans plays a
major role in the global carbon cycle.These microorganisms fix atmospheric
CO2 which is partly exported to the deep sea. In the future, marine
phytoplankton may play an important role in determining the magnitude of the
oceanic sink of anthropogenic CO2. However,the depletion of stratospheric
ozone and subsequent increase in ultraviolet (UV) irradiance at the sea
surface has been shown to affect the performance of phytoplankton
negatively.In this report, model calculations are presented of the
potential UV effect on global primary production for recent ozone layer
conditions compared to those of 18 years ago. During the appearance of the
ozone hole above the Antarctic (September-December), the calculated decrease
in dept-integrated primary production over the past 18 years amounts to 2.2
percent.In the Arctic, a decrease of up to 0.6 percent is estimated during
the period March-May. The ozone related change in total global export
production over the past decades was no more then marginal. Locally,
however, Negative effects can be significant. The maximum change in export
production appeared in November in the Southern Ocean it was lowered with
1.2% for this month. Due to many uncertainties, large errors may occur in
these kind of assessments. For instance, more information is needed about
the adaptation of algal species to UV radiation, their differential
sensitivity to UV radiation, and consequent changes in the entire ecosystem.
Further, more insight has to be gained in the role and functioning of the
biological pump, both on a spatial and temporal scale. Only then, future
developments can be predicted with some certainty.